A theoretical investigation of NO3-initiated oxidation of toluene

The NO3 hydrogen abstraction and addition with toluene have been studied in the range 298–1000 K using density functional theory and the conventional transition state theory (CTST) methods. The geometries and frequencies of the reactants, transition states, and products were performed at BHandHLYP/6-311++G(d,p) level, single point calculation for all the stationary points were carried out at CCSD(T) calculations of the optimized structures with the same basis set. Eight different reaction paths are considered corresponding to side chain, three possible ring hydrogen abstraction, and four kinds different NO3 addition. The results of the theoretical study indicate that the reaction proceeds almost exclusively through hydrogen abstraction at room temperature, and is predicted to occur dominantly at the side chain position, the calculated overall rate constant is 6.97 × 10−17 cm3 molecule−1 s−1, showing a very good agreement with available experimental data. Although negligible at low temperature, at 1000 K ring hydrogen abstraction accounts for about 32% of the total abstraction reaction, and the whole hydrogen abstraction makes up for about 99% of the total reaction above 700 K, indicating that hydrogen abstraction is the dominate channel for the NO3–toluene reaction at all temperatures, which is different from the OH–toluene reaction. This study may provide useful information on understanding the mechanistic features of NO3-initiated oxidation of toluene.